From 64341cfb72198873e963a33fd1ad46a2e3eaafd8 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Tue, 6 Mar 2018 09:49:02 +0000
Subject: [PATCH] Added State::glDrawBuffer/glReadBuffer() method to implement
 lazy state updating for glDrawBuffer and glReadBuffer

---
 include/osg/State | 11 +++++++++++
 src/osg/State.cpp | 25 +++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/include/osg/State b/include/osg/State
index 2af764bbc..c2132bdad 100644
--- a/include/osg/State
+++ b/include/osg/State
@@ -303,6 +303,14 @@ class OSG_EXPORT State : public Referenced
         /** Apply any shader composed state.*/
         void applyShaderComposition();
 
+
+        void glDrawBuffer(GLenum buffer);
+        GLenum getDrawBuffer() const { return _drawBuffer; }
+
+        void glReadBuffer(GLenum buffer);
+        GLenum getReadBuffer() const { return _readBuffer; }
+
+
         /** Set whether a particular OpenGL mode is valid in the current graphics context.
           * Use to disable OpenGL modes that are not supported by current graphics drivers/context.*/
         inline void setModeValidity(StateAttribute::GLMode mode,bool valid)
@@ -1079,6 +1087,9 @@ class OSG_EXPORT State : public Referenced
 
         ref_ptr<FrameStamp>         _frameStamp;
 
+        GLenum                      _drawBuffer;
+        GLenum                      _readBuffer;
+
         ref_ptr<const RefMatrix>    _identity;
         ref_ptr<const RefMatrix>    _initialViewMatrix;
         ref_ptr<const RefMatrix>    _projection;
diff --git a/src/osg/State.cpp b/src/osg/State.cpp
index b4f74b2da..ac20854e0 100644
--- a/src/osg/State.cpp
+++ b/src/osg/State.cpp
@@ -51,6 +51,9 @@ State::State():
     _shaderComposer = new ShaderComposer;
     _currentShaderCompositionProgram = 0L;
 
+    _drawBuffer = GL_NONE;
+    _readBuffer = GL_NONE;
+
     _identity = new osg::RefMatrix(); // default RefMatrix constructs to identity.
     _initialViewMatrix = _identity;
     _projection = _identity;
@@ -434,6 +437,28 @@ void State::reset()
 
 }
 
+void State::glDrawBuffer(GLenum buffer)
+{
+    if (_drawBuffer!=buffer)
+    {
+        #if !defined(OSG_GLES1_AVAILABLE) && !defined(OSG_GLES2_AVAILABLE) && !defined(OSG_GLES3_AVAILABLE)
+        glDrawBuffer(buffer);
+        #endif
+        _drawBuffer=buffer;
+    }
+}
+
+void State::glReadBuffer(GLenum buffer)
+{
+    if (_readBuffer!=buffer)
+    {
+        #if !defined(OSG_GLES1_AVAILABLE) && !defined(OSG_GLES2_AVAILABLE) && !defined(OSG_GLES3_AVAILABLE)
+        glReadBuffer(buffer);
+        #endif
+        _readBuffer=buffer;
+    }
+}
+
 void State::setInitialViewMatrix(const osg::RefMatrix* matrix)
 {
     if (matrix) _initialViewMatrix = matrix;